Quote:
Originally Posted by tronic72
Hi, I filled a heap of holes yesterday and came back today to find the holes in varying degrees of hardness (or softness).
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I did the same thing about a month ago, filled some holes in my little Boston Whaler. A number of items were fastened to the
hull simply using
wood screws into the upper
fiberglass layer.
I used the same procedure as I'd done dozens and dozens of times before to my sailboat over the last 20 years or so.
I started by drilling the holes significantly oversized, and then undercutting with a custom tool.
Then I weighed out the material on a small digital scale. Getting an ACCURATE 2:1 ratio with small quantities is tough, but getting a 100:44 ratio or 100:48 with the cold cure is easy if you weigh it.
(BTW, an uncle of mine was one of the inventors of 2 part epoxy, when he was a chemist working for .. Dupont?.. IIRC. He gave me some words of wisdom. He told me that as the ratio of hardener to resin gets bigger, the strength of the epoxy goes up, which makes sense, as it's the resin that gives the strength. So 2:1 is stronger than 1:1 and 5:1 is stronger still.
BUT, as the ratio grows, so does the need for accurate mixes. 1:1 would probably
work as well as it's going to if mixed 2:1. But 5:1 mixed 5.5:1 might have less than half its strength.
So I stick with System 3 2:1, rather than West 5:1, and also take the trouble to weigh it.)
Continuing my tale, I mixed in some filler, again, as I had dozens of times in the past, and filled the holes.
A day later, I fully expected it to be hard, given that the daytime temps were in the 70s and night time maybe as low as 60. I noticed no change.
A week later, it had STARTED to set, the littlest bit, maybe.
A MONTH later, it still hadn't set, it remained a sticky mess of "oatmeal".
I still had the original mixing pot around, so I took a heat gun to it to warm it. It DID warm up, no question, but never set.
I mixed up another batch, being VERY careful about the mix. A week later in warmer
weather still, it hadn't set.
So I just tossed out about $100 worth of epoxy and started on the HORRIBLE task of COMPLETELY removing the unset epoxy; the holes still had to be filled.
Now, the epoxy was about 4 years old and had gotten pretty cold a few times, temps down to 20 or so.
However, the manufacturer's website stated that neither should be a problem, cold
storage isn't an issue, neither does it "age". So I don't know what happened.
But I do have a new process; I'll buy smaller quantities and I'll fire up a test batch before doing something where failure would be .. bad.